The Digestive System

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UNIT ONE: the digestive system

Digestion breaks down larger molecules into smaller ones.
Mouth. Oesophagus is the tube that takes food from the mouth to the stomach using waves of muscle contractions called Peristalsis. Mucus is secreted from the tissues to lubricate the foods passage. Mouth. Oesophagus is the tube that takes food from the mouth to the stomach using waves of muscle contractions called Peristalsis. Mucus is secreted from the tissues to lubricate the foods passage. Many of our foods are polymers, These are large complex molecules composed of long chains of monomers – small basic units. Proteins and some carbohydrate are polymers. In carbohydrates, the monomers are monosaccharides. They contain the elements carbon, hydrogen and oxygen. In proteins the monomers are called amino acids. They contain carbon, hydrogen, oxygen and nitrogen. The polymers in our food are insoluble so they cannot be directly absorbed into our blood stream and assimilated into new products. The polymers have to be hydrolysed into smaller more coluble molecules by adding water. This process happens during digestion. Hydrolysis is catalysed by digestive enzymes.

The large intestine absorbs water, salt and minerals. Like other parts of the digestive system, it has a folded wall. This increases the surface area for absorption. Bacteria that decompose some of the undigested food are found here, in the large intestine.

The large intestine absorbs water, salt and minerals. Like other parts of the digestive system, it has a folded wall. This increases the surface area for absorption. Bacteria that decompose some of the undigested food are found here, in the large intestine.

The stomach is a small sac. It has lots of fold to accommodate up to 4l of food and liquid. The entrance and exit are controlled by sphincter muscles. The stomach walls produce gastric juice which helps break down food. It consists of hydrochloric acid (HCL) Pepsin, and mucus. It only works in...
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